Thoughts and opinions on mains purifiers please. Are they all useless, or worse introduce more noise into the system. Or are some bad and some good.

I'm having some noise related issues in my studio, some slight chuffing and light crackle through the monitors around peak loud times (dinner time), this usually goes away at night, which makes me think I might have a mains noise related issue.

The fidelity audio stuff looks like classic audiofoolery to me, which is not to say that a real filter can never help if you have a real problem, but that stuff does not seem to be designed to go in line with the gear but rather to be plugged in near the gear to be protected..... Color me very dubious.

I mean a graph of "system detail" as the dependent variable vs "Naturalness and smoothness", really? 600Hrs "Burn in time" on a mains filter? Come on!

I would note that filters are always best employed on the SOURCE of the interference, far better to put a filter of the fridge if that is where the interference is originating then on the load.

Personally I tend to view needing such things as a sign that someone has not done there job correctly.

Incidentally, be (in general) very dubious about 'surge protectors', they almost never work as advertised and can fail either silently or in "bad" ways.

A simple type 31 T200 ferrite ring and wind the mains lead through it a dozen turns is however sometimes effective (and about a tenner).

Go through all mains plugs (if you are confident with plug wiring ) and check that all wires are firmly clamped in. (also put the right mains fuse values in while you are there)A loose wire can easily cause crackles.

I think some degree of surge protection is a good standard practice these days on mains boards and a UPC with sine wave output is a very good plan for your computer.

Narrowing down a repeating problem could be more time consuming and complex especially if it originates from a neighbouring property.

I'm with Dan on this. There are situations where additional filtering is useful and even necessary, but they are extremely rare in the UK because the mains distribution system here is actually very good and usually very clean. Added to which, any competently designed equipment will incorporate adequate mains filtering in its own power supply any way.

My view is that it's better to buy quality equipment in the first place, rather than blow significant amounts of cash on dubious after-market products to try and make up for failings in badly designed equipment.

Noisy mains issues that I've experienced in the past haven't produced 'chuffs and crackles' either -- most have been clicks and buzzes...

Hugh Robjohns wrote:I'm with Dan on this. There are situations where additional filtering is useful and even necessary, but they are extremely rare in the UK because the mains distribution system here is actually very good and usually very clean. Added to which, any competently designed equipment will incorporate adequate mains filtering in its own power supply any way.

My view is that it's better to buy quality equipment in the first place, rather than blow significant amounts of cash on dubious after-market products to try and make up for failings in badly designed equipment.
Hugh

I hate to say it Hugh but the 'dubious' piece of equipment in question is a PSI A21-M. Something I would expect to be of high quality. To say I'm feeling extremely frustrated is putting it mildly. It has already been sent back once to their factory in Switzerland. They said they found the fault, replaced the components, tested it and sent it back to me. The noise isn't as bad as it was, but its still there and audible 1-1.5m away. But its specifically around peak times, the crackling is always worst around 6-9pm, without fail. Which makes me think it is partly mains quality related.

However yes, a speaker of this level should be able to filter out the noise no problems, my other PSI has never had these crackling issues.

Arksun wrote:I hate to say it Hugh but the 'dubious' piece of equipment in question is a PSI A21-M.

I was referring to 'dubious' mains filters! But I am surprised you are having trouble with the PSI monitors as, like you, I would have expected them to be well engineered (and I had no problems during the review period).

The noise isn't as bad as it was, but its still there and audible 1-1.5m away. But its specifically around peak times, the crackling is always worst around 6-9pm, without fail. Which makes me think it is partly mains quality related.

It could well be mains related -- but not necesarily getting in to the speaker's electronics through the mains cable. It could very easily be getting in via the audio cabling between your monitor controller and the speaker, or into the monitoring controller (or any up-stream equipment) itself.

Have you been able to prove definitively that it is coming in via the mains supply?

It could well be mains related -- but not necesarily getting in to the speaker's electronics through the mains cable. It could very easily be getting in via the audio cabling between your monitor controller and the speaker, or into the monitoring controller (or any up-stream equipment) itself.

Have you been able to prove definitively that it is coming in via the mains supply?

Hugh

I suppose it could somehow be airborne yes. But I'm pretty sure its not via the balanced audio cable, simply because the noise issues are there even when the audio cable isn't plugged into it!.

I also tried swapping the speakers over keeping the cables where they are, the noise issue stayed with that one speaker. This rules out both the power cable being the problem and also it being any proximity issue to other equipment. The other PSI in the opposite positioned remained a constant steady hiss.

I must say the noise is one of the very few letdowns of the PSI. Fine if using them from a distance, but not for more close up nearfield use. My older Dynaudios which were much cheaper had a much lower noise floor in general, which is great when listening to a quiet passage in a piece of music.

Arksun wrote:I'm pretty sure its not via the balanced audio cable, simply because the noise issues are there even when the audio cable isn't plugged into it!.

Not really a fair test -- you should short the hot and cold inputs to the ground pin to prevent the socket acting as an aerial!

I also tried swapping the speakers over keeping the cables where they are, the noise issue stayed with that one speaker.

Hmmm... clearly related to the specific speaker rather than the genreal design then. But it could still be an RFI problem rather than a poor mains-filtering problem. In my experience, the former is a lot more common than the latter.

Do you know what components were changed when you returned the speakers?

It just seems odd that it could be an RFI problem when the other speaker is unaffacted in exactly the same spot, surely that would have it too.

My previous Dynaudio speakers were completely unaffected in exactly the same spot as well.

I was told by PSI that "We investigated all the parts of your loudspeakers and the problem came for the amplifier board. We replaced the whole electronic part and recalibrated your monitor to get the thinnest tolerances as well."

They did indeed improve the freq response further and even the THD seems slightly lower. It sounds superb... when the audio is sufficiently loud enough to cover the noise issues. But when its a quiet section or no audio playing it sticks out like a sore thumb.

I'm sure you can apreciate a producer or engineers mind with an attention to detail its a hard thing to ignore when there's this repetative pattern of noise and crackle build up.

If this was some £200 cheapo monitor, fine. But for something of this price, I kinda expect a high standard of perfection and it may be subtle but its damn distracting!.

Arksun wrote:It just seems odd that it could be an RFI problem when the other speaker is unaffacted in exactly the same spot, surely that would have it too.

Not necessarily. RFI can get in because of a slightly higher ground impedance in part of the circuitry -- a dry joint somewhere or a tarnished earth tag, that kind of thing. Or a faulty or incorrect component could cause one of the amp stages to have a wider than intended bandwidth, or cause some HF instability that is generating the noises you're hearing. It's not as simple as it might first appear, and there's lots of opportunities for the speakrs to perform slightly differently.

My previous Dynaudio speakers were completely unaffected in exactly the same spot as well.

Entirely different design in every way, so not comparable.

I was told by PSI that "We investigated all the parts of your loudspeakers and the problem came for the amplifier board. We replaced the whole electronic part and recalibrated your monitor to get the thinnest tolerances as well."

Yes, that suggests an amplifier instability or RFI susceptibility -- and nothing at all to do with the mains!

They did indeed improve the freq response further and even the THD seems slightly lower. It sounds superb... when the audio is sufficiently loud enough to cover the noise issues. But when its a quiet section or no audio playing it sticks out like a sore thumb.

Doesn't sound like 'fit for purpose' to me -- especially since you are happy with the other speaker in the pair. Given that they've already been 'repaired' once, I'd suggest returning them for a complete replacement (or refund).

Yep, ship 'em back, the RFI might be curable externally (possibly), but they should not be susceptible in the first place.

Powered monitors are actually something of a notorious problem child for RFI issues, wooden boxes, so not screened, and IME pickup is often via the internal wiring from the amp to the loudspeaker drivers!

For some reason the guys who design the audio amps for these things always seem to 'value engineer' RFI measures at the amplifier stage OUTPUT out of the design, but a foot of speaker lead is a 1/4 wave aerial at ~250Mhz, or a couple of wavelengths at 1.8Ghz (Mobile phones!).

The fact that there is a certain section of the audiofool community who seem to think that less components is automatically better does not help in this regard, not that I suspect your boxes of having that particular foolishness applied.

Interesting stuff indeed. Would RF interference follow a pattern of being worst in the evenings (when lots of ovens, kettles etc are being used) and being much better early in day or late at night?. Because thats the pattern I have to the noise problems.

If your particular problem source is something like an oven thermostat arcing or similar (and they are a bit known for it) then sure you would only hear it when the oven was on!

Fridge thermostats are also a notorious source and will tend to kick in more when the door is being repeatedly opened (as say during a meal)....

Actually the other notorious source is boiler thermostats used in room for central heating, the inductance of the gas valve makes for a lovely inductive load that extends the arc and is very hard on the contacts and the wiring between the valve and the thermostat makes a dandy aerial.

Un suppressed heavy current switching is the thing that these things have in common, and it can stuff things up good and proper.
You think what it does to your monitors is frustrating, you want to try being an inner city short wave radio listener sometime (We hates plasma tellys we does, DC to daylight they radiates, preciousss).........

However the problem is basically the susceptibility of that speaker, not the fact that someone has a slightly faulty something that is using the mains wiring as an aerial to radiate hash.

The thing thats most frustrating is that its doing this after it was returned from repair job. They've told me now that they replaced the entire amp and they tested it for 3 whole days. As far as they're concerned there was no fault when it left the factory to be shipped back to me and I get the distinct impression they're now looking at me as a troublesome customer when it is still a very real issue.

I could well end up sending it back and they say they can't detect any fault, simply because the mains/emi/rfi interference at their factory isn't as strong as it is where I live.

It still does not change the fact however that my other PSI speaker has no extra hissing/crackling sounds and remains perfectly smooth in its hiss, nor does any of my other equipment seem affected.

So I face a very difficult choice, do I send it back with costly shipping and end up getting it back the same or charged extra for an amp replacement. Do I just live with the issue, or do I see if I can get a refund from the store it was purchased from.

Arksun wrote:Interesting stuff indeed. Would RF interference follow a pattern of being worst in the evenings (when lots of ovens, kettles etc are being used) and being much better early in day or late at night?. Because thats the pattern I have to the noise problems.

It's a long shot but quite a few years ago we had this sort of problem in Farnborough every time one specific transformer was switched in the evening. It did horrible things to VHF TV (yes it was that long ago).

However, I agree with the others. The monitor should not be susceptible - especially as the other one isn't!

An arc on one particular knacked contact on a tap changer could produce quite a lot of VHF energy, but the fact that only one does it is telling in my view (as is the fact that the other gear does NOT do it). Also a telly is designed (usually badly!) to pick up RF.

RFI is one of those areas that nobody in manufacturing wants to pay for until it bites them (And the CE standard for a device to be considered immune in a pro audio context is something utterly stupid (going from memory here) "interference must be more then 20dB below rated output!", it is not that, but it is something that asinine.

I found need for a mains 6 way of late so I bought one of the Tacima's to try out.
Seems like a very high quality product to me, I did not have any problems tbh. But
they seem nicely engineered.Feels like a belt and braces thing to do and they hardly break the bank. I have suggested a friend get one who plays out with a laptop/guitar rig in various venues.

So thanks for the heads up.

This could be complete nonsense but I could swear my TFT images have sharpened up. I have
no comment to make regarding audio as yet.

Soo, in the end I finally managed to get them to send me a totally brand new speaker unit. Thankfully this one doesn't have any of the crackling issues, phew!. Only at peak load times if I put my ear like literally an inch away from the tweeter, I can still hear some underlying noises, but as they're below the natural background hiss from the tweeter they simply aren't audible @1m distance.